This application relates to controlling power for a sleeping state of a computer.
Many IBM-compatible personal computer (PC) systems incorporate some form of power management scheme that allows the computers to enter low-power sleeping states, sometimes without losing system context. In many cases, these computers include stand-by power regulators that supply a limited amount of current to a few system components, which stand ready to wake the computers from the sleeping states. If these power regulators cut in prematurely or shut off delinquently when the computers enter or exit the sleeping states, the regulators may be forced to supply more current to system components than they are designed to supply. Drawing too much current from a stand-by power regulator may cause the regulator""s output voltage to fall below an acceptable level (i.e., to xe2x80x9ccrashxe2x80x9d) and thus prevent the computer from entering or exiting the low-power sleeping state properly.
As a computer enters or exits a sleeping state, carefully selected shut-down sequences ensure that stand-by power rails are not forced to provide power to high-power system components as these components shut down or start up. This is particularly useful, for example, in a personal computer that supports a sleeping state in which some, but not all, of the system components continue to draw current. As a result, the computer""s stand-by power rails tend not to crash as the computer enters or exits the sleeping state.
In one aspect, the invention involves receiving a sleep signal that instructs the computer to enter a sleeping state in which stand-by power from a power source is needed. A control signal initiates delivery of stand-by power from the power source in connection with the computer""s entering the sleeping state. The control signal is asserted in at least one situation in which the sleep signal is asserted, and the control signal is not asserted in at least one other situation in which the sleep signal is asserted.
Other embodiments and advantages will become apparent from the following description and from the claims.